I have a 07 Silverado Classic with the 4.8L and the last 2 weeks I have noticed that under load going up hills it will start blowing white smoke out of the exhaust and the oil fill tube. I do not notice any performance issues when this happens and it only lasts briefly and goes away. I was thinking it could possibly be the pcv valve but I had it smogged last week and it passed. Im not sure if it could pass smog with a bad pcv valve. Any ideas? I also do not see any sign of water in the oil.

 

If you didn't replace the pcv valve, I'd recommend do so

 

Do I only need to replace on one valve cover? I was at the Chey parts counter and they were saying that i need to replace both valve covers, somwthing about the fact that the pcv valve wasnt removable from the valve covers.

 

After another look it isnt smoking from exhaust it is oil getting pushed out of dipstick and smoking on engine.

 

My money is with everybody else. PCV valve. Check all of the hoses, such as PCV, EGR, vacuum, vapor recovery, etc. I'm not familiar with newer GM gas engines, since mine is a diesel, (my other is a '90 K1500 GMC 350 (I refuse to say 5.7L) but the theory is the same. If your oil level is OK (sure you have the correct dip stick and the dipstick tube is installed correctly) and you're pressurizing the crank case, either you have major piston blow-by or no ventilation. Does removing the PCV valve cause it to quit smoking? Can you feel pressure when you take off the oil filler cap and block it with your hand with the engine running? Vacuum on the PCV valve hose? Just some thoughts.